1. Field of the Invention
The present invention relates to a bone number determination apparatus for analyzing the anatomical positions of bones in medical images and a computer-readable recording medium that has stored a program for the apparatus.
2. Description of the Related Art
In recent years, in the field of medicine, a series of three-dimensional images composed of a multiplicity of tomograms (tomographic images, slice images or cross-sectional images) are obtained by scanning the human body of a patient from the chest to the groins thereof, and used for diagnosing the patient. In such diagnosis, a technique for automatically detecting the positions of vertebrae and ribs is essential to recognition of various anatomical positions in the human body of the patient.
A technique for separating vertebrae from each other is proposed, for example, in “Quantitative Evaluation of Osteoporosis Likelihood using Multi-slice CT Images”, M. Uehara et al., IEICE Technical Report, MI2005-90, pp. 97-100, 2005 (hereinafter, referred to as “Non-Patent Literature 1”). In Non-Patent Literature 1, morphology operation is performed on tomograms to extract vertebral endplates and intervertebral regions, thereby separating (segmenting) the vertebrae from each other. Further, another technique is proposed in “Using Mathematical Morphology for the Anatomical Labeling of Vertebrae from 3D CT-Scan Images”, B. Naegel, Computerized Medical Imaging and Graphics, Vol. 31, Issue 3, pp. 141-156, 2007 (hereinafter, referred to as “Non-Patent Literature 2”). In Non-Patent Literature 2, morphology operation is performed on tomograms to detect intervertebral region candidate areas. Further, intervertebral areas are detected by using projection values of pixels in the detected intervertebral region candidate areas to separate (segment) the vertebrae from each other.
Meanwhile, it is important to know the numbers of vertebrae (vertebra numbers) to accurately recognize anatomical positions in a patient. However, since the vertebrae are similar to each other, it is difficult to identify the vertebra number of a vertebra only based on the vertebra per se. When an image includes the twelfth rib and the first rib of the patient, it is possible to accurately know the rib numbers of the ribs. Therefore, the twelfth vertebra or the first vertebra is identified based on the connection between the twelfth vertebra and the twelfth rib or the connection between the first vertebra and the first rib, respectively (or based on both of the connections). Further, the vertebra numbers of other vertebrae are identified based on the twelfth vertebra or the first vertebra.
However, in the conventional techniques, in which the vertebra numbers are identified based on the connection between the twelfth rib and the vertebra or the connection between the first rib and the vertebra, if neither the twelfth rib nor the first rib is included in the image, it is impossible to identify the vertebra numbers. Further, it is impossible to identify even the rib numbers per se.